Method of embedding digital watermark, storage medium in which the method is stored, method of identifying embedded digital watermark, and apparatus for embedding digital watermark

Abstract

The procedure of the present invention specifies predetermined elements included in a matrix F which is obtained by Fourier transform of master image data P0 (step S122), and adds a minute variation ΔF of a predetermined magnitude to either a real number array FR or an imaginary number array FI of the predetermined elements (step S124 and S126). Here note that the minute variation ΔF should be subtracted from corresponding elements, in order to keep the symmetry of the Fourier spectrum. A resulting image obtained by an inverse transform of the matrix with the minute variation ΔF added thereto includes a phase difference pattern W01 that is embedded therein and corresponds to the minute variation ΔF. As long as a master image is closed to the public, this embedded pattern can not be taken out of the resulting image nor be deleted by overwriting attacks. Even if the processed data with the digital watermark embedded therein is exposed to overwriting attacks of different pieces of watermark information by the similar algorithm, the arrangement of the information enables the digital watermark embedded in the master data to be taken out accurately. The similar series of processing may be carried out with regard to a specific area of the low frequency component obtained by wavelet transform of the mater image.

Description

TECHNICAL FIELD[0001]The present invention relates to a digital watermarking technique and more specifically to a technique that embeds watermark information in data, such as image data.BACKGROUND ART[0002]A variety of digital watermarking techniques have been proposed to embed copyright information in digitalized copies of images and music. Digitalized data is readily copied in a complete form (namely, digitalized data has perfect reproducibility), so that the protecting measure is required against illegal copies. The digital watermarking technique electronically embeds watermark information, such as copyright information, in master data in a human-imperceptible manner. The embedded watermark information can be taken out according to the requirements. The digital watermark clearly shows any third party the presence of the copyright in digitalized copies of images and music. The digital watermark generally includes information for identifying the copyright holder. The data with the ...

AI Technical Summary

Benefits of technology

[0005]The object of the present invention is to solve the drawbacks of the prior art technique discussed above and thus to provide an embedding technique that ensures the good preservation of

Problems solved by technology

The prior art digital watermarking technique, however, has the drawback that the legal watermark information is not taken out accurately when another piece of information overwrites the existing information by a similar procedure.

When the authorized data is exposed to the overwriting attack to prevent the embed

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